Editorial Note on Part 571
Editorial Note: Nomenclature changes to part 571 appear at 69 FR 18803, Apr. 9, 2004.

§ 571.138 Standard No. 138; Tire pressure monitoring systems. S1 *Purpose and scope.* This standard specifies performance requirements for tire pressure monitoring systems (TPMSs) to warn drivers of significant under-inflation of tires and the resulting safety problems.
S2 *Application.* This standard applies to passenger cars, multipurpose passenger vehicles, trucks, and buses that have a gross vehicle weight rating of 4,536 kilograms (10,000 pounds) or less, except those vehicles with dual wheels on an axle, according to the phase-in schedule specified in S7 of this standard.
S3 *Definitions.* The following definitions apply to this standard: *Lightly loaded vehicle weight* means unloaded vehicle weight plus the weight of a mass of 180 kg (396 pounds), including test driver and instrumentation.
*Tire pressure monitoring system* means a system that detects when one or more of a vehicle's tires is significantly under-inflated and illuminates a low tire pressure warning telltale.
*Vehicle Placard* and *Tire inflation pressure label* mean the sources of information for the vehicle manufacturer's recommended cold tire inflation pressure pursuant to § 571.110 of this Part.
S4 *Requirements.* S4 . 1 *General.* To the extent provided in S7, each vehicle must be equipped with a tire pressure monitoring system that meets the requirements specified in S4 under the test conditions specified in S5 and the test procedures specified in S6 of this standard.
S4 . 2 *TPMS detection requirements.* The tire pressure monitoring system must: ( a ) Illuminate a low tire pressure warning telltale not more than 20 minutes after the inflation pressure in one or more of the vehicle's tires, up to a total of four tires, is equal to or less than either the pressure 25 percent below the vehicle manufacturer's recommended cold inflation pressure, or the pressure specified in the 3rd column of Table 1 of this standard for the corresponding type of tire, whichever is higher;
( b ) Continue to illuminate the low tire pressure warning telltale as long as the pressure in any of the vehicle's tires is equal to or less than the pressure specified in S4.2(a), and the ignition locking system is in the “On” (“Run”) position, whether or not the engine is running, or until manually reset in accordance with the vehicle manufacturer's instructions.
S4 . 3 *Low tire pressure warning telltale.* S4 . 3 . 1 Each tire pressure monitoring system must include a low tire pressure warning telltale that: ( a ) Is mounted inside the occupant compartment in front of and in clear view of the driver;
( b ) Is identified by one of the symbols shown for the “Low Tire Pressure” Telltale in Table 1 of Standard No. 101 (49 CFR 571.101); and
( c ) Is illuminated under the conditions specified in S4.2.
S4 . 3 . 2 In the case of a telltale that identifies which tire(s) is (are) under-inflated, each tire in the symbol for that telltale must illuminate when the tire it represents is under-inflated to the extent specified in S4.2.
S4 . 3 . 3 ( a ) Except as provided in paragraph (b) of this section, each low tire pressure warning telltale must illuminate as a check of lamp function either when the ignition locking system is activated to the “On” (“Run”) position when the engine is not running, or when the ignition locking system is in a position between “On” (“Run”) and “Start” that is designated by the manufacturer as a check position.
( b ) The low tire pressure warning telltale need not illuminate when a starter interlock is in operation.
S4 . 4 *TPMS malfunction.* ( a ) The vehicle shall be equipped with a tire pressure monitoring system that includes a telltale that provides a warning to the driver not more than 20 minutes after the occurrence of a malfunction that affects the generation or transmission of control or response signals in the vehicle's tire pressure monitoring system. The vehicle's TPMS malfunction indicator shall meet the requirements of either S4.4(b) or S4.4(c).
( b ) *Dedicated TPMS malfunction telltale.* The vehicle meets the requirements of S4.4(a) when equipped with a dedicated TPMS malfunction telltale that: ( 1 ) Is mounted inside the occupant compartment in front of and in clear view of the driver;
( 2 ) Is identified by the word “TPMS” as described under the “Tire Pressure Monitoring System Malfunction” Telltale in Table 1 of Standard No. 101 (49 CFR 571.101);
( 3 ) Continues to illuminate the TPMS malfunction telltale under the conditions specified in S4.4(a) for as long as the malfunction exists, whenever the ignition locking system is in the “On” (“Run”) position; and
( 4 ) ( i ) Except as provided in paragraph (ii), each dedicated TPMS malfunction telltale must be activated as a check of lamp function either when the ignition locking system is activated to the “On” (“Run”) position when the engine is not running, or when the ignition locking system is in a position between “On” (“Run”) and “Start” that is designated by the manufacturer as a check position.
( ii ) The dedicated TPMS malfunction telltale need not be activated when a starter interlock is in operation.
( c ) *Combination low tire pressure/TPMS malfunction telltale.* The vehicle meets the requirements of S4.4(a) when equipped with a combined Low Tire Pressure/TPMS malfunction telltale that: ( 1 ) Meets the requirements of S4.2 and S4.3; and
( 2 ) Flashes for a period of at least 60 seconds but no longer than 90 seconds upon detection of any condition specified in S4.4(a) after the ignition locking system is activated to the “On” (“Run”) position. After each period of prescribed flashing, the telltale must remain continuously illuminated as long as a malfunction exists and the ignition locking system is in the “On” (“Run”) position. This flashing and illumination sequence must be repeated each time the ignition locking system is placed in the “On” (“Run”) position until the situation causing the malfunction has been corrected. Multiple malfunctions occurring during any ignition cycle may, but are not required to, reinitiate the prescribed flashing sequence.
S4 . 5 *Written instructions.* ( a ) Beginning on September 1, 2006, the owner's manual in each vehicle certified as complying with S4 must provide an image of the Low Tire Pressure Telltale symbol (and an image of the TPMS Malfunction Telltale warning (“TPMS”), if a dedicated telltale is utilized for this function) with the following statement in English: Each tire, including the spare (if provided), should be checked monthly when cold and inflated to the inflation pressure recommended by the vehicle manufacturer on the vehicle placard or tire inflation pressure label. (If your vehicle has tires of a different size than the size indicated on the vehicle placard or tire inflation pressure label, you should determine the proper tire inflation pressure for those tires.) As an added safety feature, your vehicle has been equipped with a tire pressure monitoring system (TPMS) that illuminates a low tire pressure telltale when one or more of your tires is significantly under-inflated. Accordingly, when the low tire pressure telltale illuminates, you should stop and check your tires as soon as possible, and inflate them to the proper pressure. Driving on a significantly under-inflated tire causes the tire to overheat and can lead to tire failure. Under-inflation also reduces fuel efficiency and tire tread life, and may affect the vehicle's handling and stopping ability. Please note that the TPMS is not a substitute for proper tire maintenance, and it is the driver's responsibility to maintain correct tire pressure, even if under-inflation has not reached the level to trigger illumination of the TPMS low tire pressure telltale. [The following paragraph is required for all vehicles certified to the standard starting on September 1, 2007 and for vehicles voluntarily equipped with a compliant TPMS MIL before that time.] Your vehicle has also been equipped with a TPMS malfunction indicator to indicate when the system is not operating properly. [For vehicles with a dedicated MIL telltale, add the following statement: The TPMS malfunction indicator is provided by a separate telltale, which displays the symbol “TPMS” when illuminated.] [For vehicles with a combined low tire pressure/MIL telltale, add the following statement: The TPMS malfunction indicator is combined with the low tire pressure telltale. When the system detects a malfunction, the telltale will flash for approximately one minute and then remain continuously illuminated. This sequence will continue upon subsequent vehicle start-ups as long as the malfunction exists.] When the malfunction indicator is illuminated, the system may not be able to detect or signal low tire pressure as intended. TPMS malfunctions may occur for a variety of reasons, including the installation of replacement or alternate tires or wheels on the vehicle that prevent the TPMS from functioning properly. Always check the TPMS malfunction telltale after replacing one or more tires or wheels on your vehicle to ensure that the replacement or alternate tires and wheels allow the TPMS to continue to function properly.
( b ) The owner's manual may include additional information about the time for the TPMS telltale(s) to extinguish once the low tire pressure condition or the malfunction is corrected. It may also include additional information about the significance of the low tire pressure warning telltale illuminating, a description of corrective action to be undertaken, whether the tire pressure monitoring system functions with the vehicle's spare tire (if provided), and how to use a reset button, if one is provided.
( c ) If a vehicle does not come with an owner's manual, the required information shall be provided in writing to the first purchaser of the vehicle.
S5 *Test conditions.* S5 . 1 *Ambient temperature.* The ambient temperature is between 0 °C (32 °F) and 40 °C (104 °F).
S5 . 2 *Road test surface.* Compliance testing is conducted on any portion of the Southern Loop of the Treadwear Test Course defined in appendix A and Figure 2 of section 575.104 of this chapter. The road surface is dry during testing.
S5 . 3 *Vehicle conditions.* S5 . 3 . 1 *Test weight.* The vehicle may be tested at any weight between its lightly loaded vehicle weight and its gross vehicle weight rating (GVWR) without exceeding any of its gross axle weight ratings.
S5 . 3 . 2 *Vehicle speed.* The vehicle's TPMS is calibrated and tested at speeds between 50 km/h (31.1 mph) and 100 km/h (62.2 mph). For vehicles equipped with cruise control, cruise control is not to be engaged during testing.
S5 . 3 . 3 *Rim position.* The vehicle rims may be positioned at any wheel position, consistent with any related instructions or limitations in the vehicle owner's manual.
S5 . 3 . 4 *Stationary location.* The vehicle's tires are shaded from direct sun when the vehicle is parked.
S5 . 3 . 5 *Brake pedal application.* Driving time shall not accumulate during service brake application.
S5 . 3 . 6 *Range of conditions or test parameters.* Whenever a range of conditions or test parameters is specified in this standard, the vehicle must meet applicable requirements when tested at any point within the range.
S5 . 3 . 7 *Tires.* The vehicle is tested with the tires installed on the vehicle at the time of initial vehicle sale, excluding the spare tire (if provided). However, the spare tire may be utilized for TPMS malfunction testing purposes.
S6 *Test procedures.* ( a ) Inflate the vehicle's tires to the cold tire inflation pressure(s) provided on the vehicle placard or the tire inflation pressure label.
( b ) With the vehicle stationary and the ignition locking system in the “Lock” or “Off” position, activate the ignition locking system to the “On” (“Run”) position or, where applicable, the appropriate position for the lamp check. The tire pressure monitoring system must perform a check of lamp function for the low tire pressure telltale as specified in paragraph S4.3.3 of this standard. If the vehicle is equipped with a separate TPMS malfunction telltale, the tire pressure monitoring system also must perform a check of lamp function as specified in paragraph S4.4(b)(4) of this standard.
( c ) If applicable, set or reset the tire pressure monitoring system in accordance with the instructions in the vehicle owner's manual.
( d ) *System calibration/learning phase.* ( 1 ) Drive the vehicle for up to 15 minutes of cumulative time (not necessarily continuously) along any portion of the test course.
( 2 ) Reverse direction on the course and drive the vehicle for an additional period of time for a total cumulative time of 20 minutes (including the time in S6(d)(1), and not necessarily continuously).
( e ) Stop the vehicle and deflate any combination of one to four tires until the deflated tire(s) is (are) at 7 kPa (1 psi) below the inflation pressure at which the tire pressure monitoring system is required to illuminate the low tire pressure warning telltale.
( f ) *System detection phase.* ( 1 ) Within 5 minutes of reducing the inflation pressure in the tire(s), drive the vehicle for up to 10-15 minutes of cumulative time (not necessarily continuously) along any portion of the test course.
( 2 ) Reverse direction on the course and drive the vehicle for an additional period of time for a total cumulative time of 20 minutes (including the time in S6(f)(1), and not necessarily continuously).
( 3 ) The sum of the total cumulative drive time under paragraphs S6(f)(1) and (2) shall be the lesser of 20 minutes or the time at which the low tire pressure telltale illuminates.
( 4 ) If the low tire pressure telltale did not illuminate, discontinue the test.
( g ) If the low tire pressure telltale illuminated during the procedure in paragraph S6(f), deactivate the ignition locking system to the “Off” or “Lock” position. After a 5-minute period, activate the vehicle's ignition locking system to the “On” (“Run”) position. The telltale must illuminate and remain illuminated as long as the ignition locking system is in the “On” (“Run”) position.
( h ) Keep the vehicle stationary for a period of up to one hour with the engine off.
( i ) Inflate all of the vehicle's tires to the same inflation pressure used in paragraph S6(a). If the vehicle's tire pressure monitoring system has a manual reset feature, reset the system in accordance with the instructions specified in the vehicle owner's manual. Determine whether the telltale has extinguished. If necessary, drive the vehicle until the telltale has been extinguished.
( j ) The test may be repeated, using the test procedures in paragraphs S6(a)-(b) and S6(d)-(i), with any one, two, three, or four of the tires on the vehicle under-inflated.
( k ) Simulate one TPMS malfunction by disconnecting the power source to any TPMS component, disconnecting any electrical connection between TPMS components, or installing a tire or wheel on the vehicle that is incompatible with the TPMS. When simulating a TPMS malfunction, the electrical connections for the telltale lamps are not to be disconnected.
( l ) *TPMS malfunction detection.* ( 1 ) Drive the vehicle for up to 15 minutes of cumulative time (not necessarily continuously) along any portion of the test course.
( 2 ) Reverse direction on the course and drive the vehicle for an additional period of time for a total cumulative time of 20 minutes (including the time in S6(l)(1), and not necessarily continuously).
( 3 ) The sum of the total cumulative drive time under paragraphs S6(l)(1) and (2) shall be the lesser of 20 minutes or the time at which the TPMS malfunction telltale illuminates.
( 4 ) If the TPMS malfunction indicator did not illuminate in accordance with paragraph S4.4, as required, discontinue the test.
( m ) If the TPMS malfunction indicator illuminated during the procedure in paragraph S6(l), deactivate the ignition locking system to the “Off” or “Lock” position. After a 5-minute period, activate the vehicle's ignition locking system to the “On” (“Run”) position. The TPMS malfunction indicator must again signal a malfunction and remain illuminated as long as the ignition locking system is in the “On” (“Run”) position.
( n ) Restore the TPMS to normal operation. If necessary, drive the vehicle until the telltale has extinguished.
( o ) The test may be repeated using the test procedures in paragraphs S6(k)-(n), with each such test limited to simulation of a single malfunction.
S7 *Phase-in schedule.* S7 . 1 *Vehicles manufactured on or after October 5, 2005, and before September 1, 2006.* For vehicles manufactured on or after October 5, 2005, and before September 1, 2006, the number of vehicles complying with this standard (except for the provisions of S4.4 unless the manufacturer elects to also certify to those provisions) must not be less than 20 percent of: ( a ) The manufacturer's average annual production of vehicles manufactured on or after September 1, 2002, and before October 5, 2005; or
( b ) The manufacturer's production on or after October 5, 2005, and before September 1, 2006.
S7 . 2 *Vehicles manufactured on or after September 1, 2006, and before September 1, 2007.* For vehicles manufactured on or after September 1, 2006, and before September 1, 2007, the number of vehicles complying with this standard (except for the provisions of S4.4 unless the manufacturer elects to also certify to those provisions) must not be less than 70 percent of: ( a ) The manufacturer's average annual production of vehicles manufactured on or after September 1, 2003, and before September 1, 2006; or
( b ) The manufacturer's production on or after September 1, 2006, and before September 1, 2007.
S7 . 3 *Vehicles manufactured on or after September 1, 2007.* Except as provided in S7.7, all vehicles manufactured on or after September 1, 2007 must comply with all requirements of this standard.
S7 . 4 *Calculation of complying vehicles.* ( a ) *Carry-Forward Credits.* For purposes of complying with S7.1, a manufacturer may count a vehicle if it is certified as complying with this standard and is manufactured on or after April 8, 2005, but before September 1, 2006.
( b ) For purposes of complying with S7.2, a manufacturer may count a vehicle if it: ( 1 ) ( i ) Is certified as complying with this standard and is manufactured on or after April 8, 2005, but before September 1, 2007; and
( ii ) Is not counted toward compliance with S7.1; or
( 2 ) Is manufactured on or after September 1, 2006, but before September 1, 2007.
( c ) *Carry-Backward Credits.* At the vehicle manufacturer's option, for purposes of complying with S7.1, a manufacturer may count a vehicle it plans to manufacture and to certify as complying with this standard that will be produced on or after September 1, 2006 but before September 1, 2007. However, a vehicle counted toward compliance with S7.1 may not be counted toward compliance with S7.2. If the vehicle manufacturer decides to exercise the option for carry-backward credits, the manufacturer must indicate this in its report for the production period corresponding to S7.1 filed pursuant to 49 CFR 585.66. The vehicles are counted in fulfillment of the requirements of S7.1, subject to actually being produced in compliance with this standard during the specified time period and not being counted toward the requirements of S7.2.
S7 . 5 *Vehicles produced by more than one manufacturer.* S7 . 5 . 1 For the purpose of calculating average annual production of vehicles for each manufacturer and the number of vehicles manufactured by each manufacturer under S7.1 through S7.3, a vehicle produced by more than one manufacturer must be attributed to a single manufacturer as follows, subject to S7.5.2: ( a ) A vehicle that is imported must be attributed to the importer.
( b ) A vehicle manufactured in the United States by more than one manufacturer, one of which also markets the vehicle, must be attributed to the manufacturer that markets the vehicle.
S7 . 5 . 2 A vehicle produced by more than one manufacturer must be attributed to any one of the vehicle's manufacturers specified by an express written contract, reported to the National Highway Traffic Safety Administration under 49 CFR part 585, between the manufacturer so specified and the manufacturer to which the vehicle would otherwise be attributed under S7.5.1.
S7 . 6 *Small volume manufacturers.* Vehicles manufactured by a manufacturer that produces fewer than 5,000 vehicles for sale in the United States during the period of September 1, 2005 to August 31, 2006, or the period from September 1, 2006 to August 31, 2007, are not subject to the corresponding requirements of S7.1, S7.2, and S7.4.
S7 . 7 *Final-stage manufacturers and alterers.* Vehicles that are manufactured in two or more stages or that are altered (within the meaning of 49 CFR 567.7) after having previously been certified in accordance with part 567 of this chapter are not subject to the requirements of S7.1 through S7.4. Instead, vehicles that are manufactured in two or more stages or that are altered must comply with this standard beginning on September 1, 2008.
Tables to § 571.138 Table 1—Low Tire Pressure Warning Telltale—Minimum Activation Pressure
Column 1—tire type
Column 2—maximum or rated inflation pressure
Column 3—minimumactivation pressure (kPa)
(psi)
(kPa)
(psi) P-metric—Standard Load
240,300, or350
35,44, or51
140140140
202020 P-metric—Extra Load
280 or340
41 or49
160160
2323 Load Range C
350
51
200
29 Load Range D
450
65
240
35 Load Range E
550
80
240
35
[70 FR 18187, Apr. 8, 2005, as amended at 70 FR 53100, Sept. 7, 2005; 72 FR 38025, July 12, 2007]